Hello ckangell,
Thanks for contacting us!
Unfortunately that level of customization typically goes beyond the scope of the forums.
However with a little coding, this blog post should put you on the right path https://theeventscalendar.com/how-to-add-events-to-your-rss-feed/
Look at the second half of the post, where you add start date/time. Replace that information with ‘the_post_thumbnail()’ instead, and it should work.
These are only high level tips, you’ll need to do some troubleshooting. But if you have questions that are in the scope of the forum I’d be happy to help!
Cheers!
– Casey Driscoll